MySql三种避免重复插入数据的方法

前言

MySql 在存在主键冲突或唯一键冲突的情况下,根据插入方式,一般有以下三种插入方式避免错误。

  1. insert ignore。
  2. replace into
  3. insert>insert ignore

    insert ignore 会忽视数据库中已经存在的数据,根据主键或者唯一索引判断,如果数据库没有数据,就会插入新的数据,如果有数据的话就跳过这条数据

    小case

    表结构

    root:test> show create table t3G
    *************************** 1. row ***************************
      Table: t3
    Create Table: CREATE TABLE `t3` (
     `id` int(11) NOT NULL AUTO_INCREMENT,
     `c1` int(11) DEFAULT NULL,
     `c2` varchar(20) DEFAULT NULL,
     `c3` int(11) DEFAULT NULL,
     PRIMARY KEY (`id`),
     UNIQUE KEY `uidx_c1` (`c1`)
    ) ENGINE=InnoDB AUTO_INCREMENT=18 DEFAULT CHARSET=utf8
    1 row in set (0.00 sec)
    
    root:test> select * from t3;
     +----+------+------+------+
     | id | c1 | c2 | c3 |
     +----+------+------+------+
     | 1 | 1 | a | 1 |
     | 2 | 2 | a | 1 |
     | 8 | NULL | NULL | 1 |
     | 14 | 4 | bb | NULL |
     | 17 | 5 | cc | 4 |
     +----+------+------+------+
     5 rows in set (0.00 sec)

    插入冲突数据

    root:test> insert ignore into t3 (c1,c2,c3) values(5,'cc',4),(6,'dd',5);  Query OK, 1 row affected, 1 warning (0.01 sec)
    Records: 2 Duplicates: 1 Warnings: 1

    查看结果

    root:test> show warnings;
    +---------+------+---------------------------------------+
    | Level | Code | Message        |
    +---------+------+---------------------------------------+
    | Warning | 1062 | Duplicate entry '5' for key 'uidx_c1' |
    +---------+------+---------------------------------------+
    1 row in set (0.00 sec)
    
    root:test> select * from t3;
    +----+------+------+------+
    | id | c1 | c2 | c3 |
    +----+------+------+------+
    | 1 | 1 | a | 1 |
    | 2 | 2 | a | 1 |
    | 8 | NULL | NULL | 1 |
    | 14 | 4 | bb | NULL |
    | 17 | 5 | cc | 4 |
    | 18 | 6 | dd | 5 |
    +----+------+------+------+
    6 rows in set (0.00 sec)

    replace into

    replace into 会尝试先插入数据,如果发现冲突进行删除。否则不做任何操作。

    小case

    root:test> show create table t3G
    *************************** 1. row ***************************
      Table: t3
    Create Table: CREATE TABLE `t3` (
     `id` int(11) NOT NULL AUTO_INCREMENT,
     `c1` int(11) DEFAULT NULL,
     `c2` varchar(20) DEFAULT NULL,
     `c3` int(11) DEFAULT NULL,
     PRIMARY KEY (`id`),
     UNIQUE KEY `uidx_c1` (`c1`)
    ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8
    1 row in set (0.00 sec)
    
    root:test> select * from t3;
    +----+------+--------+------+
    | id | c1 | c2  | c3 |
    +----+------+--------+------+
    | 1 | 1 | cc  | 4 |
    | 2 | 2 | dd  | 5 |
    | 3 | 3 | qwewqe | 3 |
    +----+------+--------+------+
    3 rows in set (0.00 sec)

    插入冲突数据

    root:test> replace into t3 (c1,c2,c3) values(3,'new',8);
    Query OK, 2 rows affected (0.02 sec)
    
    root:test> select * from t3;
    +----+------+------+------+
    | id | c1 | c2 | c3 |
    +----+------+------+------+
    | 1 | 1 | cc | 4 |
    | 2 | 2 | dd | 5 |
    | 4 | 3 | new | 8 |
    +----+------+------+------+
    3 rows in set (0.00 sec)

    可以看到原有的记录已经没有了,新的记录又有了。

    insert> root:test> show create table t3G *************************** 1. row *************************** Table: t3 Create Table: CREATE TABLE `t3` ( `id` int(11) NOT NULL AUTO_INCREMENT, `c1` int(11) DEFAULT NULL, `c2` varchar(20) DEFAULT NULL, `c3` int(11) DEFAULT NULL, PRIMARY KEY (`id`), UNIQUE KEY `uidx_c1` (`c1`) ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 1 row in set (0.00 sec) root:test> select * from t3; +----+------+------+------+ | id | c1 | c2 | c3 | +----+------+------+------+ | 1 | 1 | fds | 4 | | 2 | 2 | ytu | 3 | | 3 | 3 | czx | 5 | +----+------+------+------+ 3 rows in set (0.00 sec)

    插入一条与记录id=3存在唯一键(列c1)冲突的数据

    root:test> insert into t3(c1,c2,c3) values (3,'new',5) on duplicate key update c1=c1+3; 
    Query OK, 2 rows affected (0.01 sec)
    
    root:test> select * from t3;
    +----+------+------+------+
    | id | c1 | c2 | c3 |
    +----+------+------+------+
    | 1 | 1 | fds | 4 |
    | 2 | 2 | ytu | 3 |
    | 3 | 6 | czx | 5 |
    +----+------+------+------+
    3 rows in set (0.00 sec)

    可以看到,id=3的记录发生了改变,c1=原有的c1+3,其他列没有改变。

    以上就是MySql四种避免重复插入数据的方法的详细内容,更多关于MySQL 避免插入重复数据的资料请关注我们其它相关文章!

    MySql三种避免重复插入数据的方法

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